Structural plumage colour and parasites in satin bowerbirdsPtilonorhynchus violaceus: implications for sexual selection

Abstract

Doucet, S. M. and Montgomerie, R. 2003. Structural plumage colour and parasites in satin bowerbirds Ptilonorhynchus 6iolaceus: implications for sexual selection. -J. Avian Biol. 34: 237-242.We investigated whether variation in structural plumage coloration in satin bowerbirds, Ptilonorhynchus 6iolaceus, could reveal the intensity of infection from parasites, as predicted from models of parasite-mediated sexual selection (PMSS). To do this, we captured adult male, female, and juvenile male satin bowerbirds in Queensland, Australia, and objectively measured individual plumage reflectance from four body regions using a spectrometer. We quantified both ectoparasite load and the intensity of infection from blood parasites. In iridescent blue adult males, plumage reflectance is unimodal, with a single peak in the ultraviolet, while in greenish females and juveniles, plumage reflectance is bimodal, with peaks in both the ultraviolet and green portions of the spectrum. In adult males, the intensity of infection from blood parasites was best predicted by plumage brightness (total reflectance), with brighter males having fewer parasites. Similarly, juvenile males exhibiting greater UV chroma (proportion of reflectance in the UV) had fewer blood parasites. Our findings support a key prediction of PMSS models and provide the first evidence that a structural colour ornament can signal the intensity of infection from blood parasites.

Pterin pigments amplify iridescent ultraviolet signal in males of the orange sulphur butterfly,Colias eurytheme

“…Investigations of colouration as honest signals of quality have focused primarily on pigment-based colouration (Hamilton & Zuk 1982;Lozano 1994;Olsen & Owens 1998;Hill 1999;McGraw & Hill 2000;Grether et al 2001;Blount et al 2003), but structural colours are being studied with increasing frequency from this perspective ( Johnsen et al 1998( Johnsen et al , 2003Keyser & Hill 1999;McGraw et al 2002;Doucet & Montgomerie 2003;Siefferman & Hill 2003). Most animal colours, however, are generated through a combined effects of these mechanisms.…”

The signaling function of plumage characteristics in female tree swallows and implications for reproductive success and life-history decisions.

“…The plumage colouration of tree swallows is structural-based, and evidence is accruing for the condition-dependence and thus honest-signaling potential of structural plumage colouration in birds (Hill 2006b). To date, most studies examining structural plumage colouration have found that plumage brightness and UV-blue colouration are reduced in individuals that suffer from nutritional stress (Siefferman and Hill 2005a) and parasitic infection (Doucet and Montgomerie 2003), and that less colourful, duller individuals have lowered reproductive success (Siefferman and Hill 2005a;Doutrelant et al 2008). I found that more UV-blue, brighter females had higher levels of parasitism ( contrary to what would be expected if only high quality individuals can produce these potentially costly plumage traits (Zahavi 1975;Hamilton and Zuk 1982;Kodric-Brown and Brown 1984).…”

“…Developmental perturbations, however, may cause variation in the number or thickness of the feather nanostructures and could affect the brightness and colour of the feather (Prum 2006). In fact, studies have found that variation in the hue and brightness of structurally-coloured feathers is related to the nutritional status (Keyser and Hill 1999) and physiological condition of the bearer (Doucet and Montgomerie 2003). If these nanostructures are costly to produce (Shawkey et al 2003;Doucet et al 2006), this may be the physiological mechanism allowing structural plumage colouration to be an honest indicator of individual quality.…”

“…Only recently has structural plumage colouration received attention as a condition-dependent signal. Studies have found that variation in structurally-coloured plumage is related to the nutritional status (Keyser and Hill 1999) and physiological condition of the bearer (Doucet and Montgomerie 2003), potentially due to the costly nature of producing fine nanoscale feather structures (Shawkey et al 2003;Doucet et al 2006). Bitton et al (2008) examined the potential signaling function of structural plumage colouration in female tree swallows (Tachycineta bicolor), and found that ultraviolet (UV) -blue colouration and plumage brightness were related to reproductive success and were potentially sexually selected traits.…”

Anting behavior by the White-bearded Manakin (Manacus manacus, Pipridae): an example of functional interaction in a frugivorous lekking bird

“…Regarding all factors that may drive the attractiveness of males, individuals that have better external and physical conditions will compete more efficiently for females (Kirkpatrick & Ryan 1991). Ectoparasites signalize the current health condition of birds, and affect negatively the fitness of males by increasing the cost of antiparasite effects in their immune system, causing loss of blood, infections, and diseases (Price 1980, de Lope et al 1993, Doucet & Montgomerie 2003. Additionally, females are able to enhance the viability of their offspring by choosing males with better physical conditions as an indicator of relative resistance to parasites (Hamilton & Zuk 1982).…”